The present invention is directed to the field of network communications, particularly those of the type conducted over a wireless local area network (WLAN). Multicasting is widely used to send transmissions to a select group of recipients. IP multicasting allows a single set of packets to be transmitted to a plurality of recipients over the Internet, unlike typical Internet transmissions in which a source connects to a single recipient destination. IP multicast applications such as streaming audio/video multicasts are becoming increasingly widespread. As a consequence, the volume of IP multicast traffic is increasing.
By default, all multicast traffic is distributed throughout a local area network (LAN). However, multicast transmissions can be especially problematic when used in WLANs that provide wireless access in accordance with the IEEE 802.11 standards. Due to the network architecture of a WLAN, multicast transmissions are forwarded by a wireless “access point” to a “client”, i.e. a user station, through the air via radio frequency transmission. Since multicast transmissions are forwarded by a plurality of 802.11 access points, they therefore consume more wireless bandwidth than single data stream unicast transmissions.
A wireless access point under the IEEE 802.11 protocol is typically connected to a high-speed Ethernet link having a bandwidth of 100 Mbps (megabits per second). However, due to certain limitations in wireless transmission, an 802.11 access point operates at a much lower bandwidth, typically about 2–11 Mbps. Consequently, multicast transmissions are typically rate-limited to control the amount of bandwidth consumed for multicast traffic. However, such rate-limiting creates problems in transmission that can create errors.
Select packets from the wired network have a destination multicast address enabled by an 802.11 station. Such packets are deemed “useful” by the access point, and packets lacking such an enabled address are deemed “useless.” If simple rate limiting is used to restrict the amount of multicast traffic on 802.11 links by the access point, it may happen that both “useless” and “useful” packets may be discarded. This can result in signal dropouts in the multicast transmissions, or even a complete transmission failure, resulting in inconvenience and dissatisfaction on the part of the network user.